Transcript Dwarf Planets

Dwarf Planets
Solar System Debris
Dwarf Planets
• Three criteria:
– Orbits the Sun directly
– Massive enough to be rounded by its own gravity
– Has not cleared the smaller bodies from its orbit
Ceres
• Found in the asteroid belt
• Once considered the largest asteroid
Ceres - The numbers
– Contains 1/3 the total mass of all the asteroids
– Orbital Period: 4.6 years
– Diameter: 950 Km
– Semi-major axis: 2.8 AU
– Temperature: 167 K
Ceres – Discovery
• Possibility of its existence first suggested in
1772
• Discovered in 1801 by Giuseppe Piazzi
• Named for the Roman goddess
of plants
Ceres - Characteristics
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Surface like a C-class asteroid
Possibly differentiated interior?
Bright spot of unknown composition
Possible tenuous atmosphere and frost
The Dawn Mission
• Will study
asteroids
Vesta and
Ceres
• Will arrive at
Vesta in July
2011
• Will arrive at
Ceres in
February 2015
Kuiper Belt Objects (KBO)
• AKA: Trans-Neptunian Objects (TNO)
• Comet-like material
Most dwarf planets are TNOs
• Pluto – discovered on February 18, 1930,
– classified as a planet for 76 years.
– Reclassified dwarf planet : August 24, 2006.
• Eris – discovered January 5, 2005
– . Called the "tenth planet" in media reports
– Accepted as a dwarf planet : September 13, 2006.
• Makemake – discovered on March 31, 2005.
– Accepted as a dwarf planet on July 11, 2008.
• Haumea – discovered on December 28, 2004.
– Accepted as a dwarf planet on September 17,
2008.
Pluto
• Considered the 9th planet from 1930 to 2006
• Became the first dwarf planet in 2006
• Named for Roman god of the underworld
Pluto - Discovery
• Observations of Neptune
showed that something
was perturbing its orbit
• In 1906 the Lowell
Observatory began a
search for “Planet X”
• Clyde Tombaugh
discovered Pluto in 1930
using a blink comparator
Pluto - Discovery
Pluto - The numbers
– Orbital Period: 248 years
– Diameter: 2300 Km
– Semi-major axis: 39 AU
– Temperature: 44 K
– 3 known moons
• Charon : more than ½ the size of Pluto
• Nix
• Hydra
Pluto – The Orbit
• Highly eccentric
• Tilted 17º from ecliptic
Eris
• Largest dwarf planet in
solar system
• 27% more massive than
Pluto
• Named for Greek goddess
of discord
Eris - Discovery
• Discovered in 2005 by
Mike Brown at
CalTech
• Originally referred to
as the “10th planet”
• Originally named
Xena
Eris? Really?
Eris – The numbers
– Orbital Period: 557 years
– Diameter: 2400? Km
– Semi-major axis: 68 AU
– Temperature: 42.5 K
– 1 known moon
• Dysnomia
Other Potential Dwarf Planets
Pluto’s Demise